Disruption of short-duration timing associated with damage to the suprachiasmatic region of the hypothalamus.

Abstract

The neural bases of circadian rhythmicity have been demonstrated in a variety of animal species, including primates. Yet, the brain mechanisms underlying time experience and the timing of behaviors of shorter duration are still not well understood. In the present study, we demonstrate disruption of short-duration timing capacity in AH, a patient with damage to the suprachiasmatic (SCN) region of the hypothalamus. AH exhibited extreme inconsistency in her rate of tapping production on a motor continuation paradigm. Her inter-response intervals (IRIs) were extremely large compared with normal control subjects and were similar to those previously reported in patients with cerebellar dysfunction. Increased variability of both central timing and motor implementation processes was evident compared with both age-matched and elderly normal control subjects. Severe impairment of time perception was also evident on duration discrimination, whereas auditory loudness discrimination was intact. These findings suggest that a hierarchic relationship between long-duration (circadian) and short-duration timing exists, and that in addition to the cerebellum, intact hypothalamic functioning is necessary for short-duration timing.